Headlights are dim

[67 GTX]

Voltage at my headlights (could only check high beams) are only at 7 volts, causing them to be very dim.

I have begun troubleshooting. The headlight switch is removed, so that is removed from the equation.

I found the two power terminals in the headlight switch plug, and jumped them till the headlights came on, trying both power terminals (not to each other). Voltage was 7 at the lights, which was the same as when the entire system was assembled.

Possible issues:
Corrosion in foot high/low beams switch. Switch works, but perhaps corrosion built up causing a lot of resistance?

Issue in firewall plug. I think this is unlikely, since i had that plug off last year and cleaned all the contacts.

Issue in the fuse box. Could be at the fuse itself, with the contacts corroded, or at the contact going to the box itself.

Corrosion on the lights themselves, although I find this unlikely since both lights had the same voltage going to them.

Has anyone else experienced this issue and/or can suggest something that I missed or haven't mentioned?

 

[khryslerkid]

Grounds, grounds, grounds!

Is the battery voltage up?

 

[robedanb]

Voltage at my headlights (could only check high beams) are only at 7 volts, causing them to be very dim.

I have begun troubleshooting. The headlight switch is removed, so that is removed from the equation.

I found the two power terminals in the headlight switch plug, and jumped them till the headlights came on, trying both power terminals (not to each other). Voltage was 7 at the lights, which was the same as when the entire system was assembled.

Possible issues:
Corrosion in foot high/low beams switch. Switch works, but perhaps corrosion built up causing a lot of resistance?

Issue in firewall plug. I think this is unlikely, since i had that plug off last year and cleaned all the contacts.

Issue in the fuse box. Could be at the fuse itself, with the contacts corroded, or at the contact going to the box itself.

Corrosion on the lights themselves, although I find this unlikely since both lights had the same voltage going to them.

Has anyone else experienced this issue and/or can suggest something that I missed or haven't mentioned?

Same problem with my 1969 RR. Previous owners put in Halogen lights that draw more current. I had 9.5 volts at the high beams. Original wiring is 18GA. Too light. Voltage drop was throughout entire circuit. I wired in relays for low and high beam lights with 10GA wiring to the lights and ground circuits. There are also kits available to do this.

 

[Billccm]

PM @Crackedback. He sells a nice relay kit.

 

[FrnkNsteen]

Grounds, grounds, grounds!

Is the battery voltage up?

What he said! Before you go digging too deep. Wondering what the voltage from your alternator is, and if the regulator is working properly.

If all that checks out, I can also recommend the kit Crackedback sells. I put one of his kits in my Barracuda and thought it worked well. Though if your voltage is that low, something else is going on and the relay kit is just something I would do after you get the voltage back up in the 12V range.

 

[67 GTX]

The voltage at the battery is 12.6, and 13.3 when the engine is running.

I do have halogen's on the car (installed by a previous owner), but my Dad who is having the same issue on his car, has the original headlights.

I did check the grounding screw in the radiator support, and it seemed fine. But I cleaned it just to make sure.

 

[Billccm]

Easy way to prove voltage drop. Negative meter lead on lamp pin, positive meter lead to battery post. If you measure greater than 2 volts drop you have a connection issue and grounds are not an issue.
Friends 1959 el Camino had 9v at headlight pin. He replaced everything and only a relay kit solved the problem.

 

[ckessel]

Every place there is a connection/terminal etc can have a voltage drop due to age/condition leaving you without enough voltage at the other end. Add in sketchy grounds and most likely not enough of them. Time to punt the old wiring and install new stuff otherwise you'll be chasing your tail with issues for a long time. Save the molded plugs off the old stuff for fixes and can the rest. While you are updating, put new switches in, update stuff like lighting with relay packages and heavier gauge wiring, charge system, add extra grounds in with heavier gauge, clean paint/rust off ground connections and use star type lock washers to help bite in with a dab of silicone grease to prevent corrosion at that point.

 

[threewood]

PM @Crackedback. He sells a nice relay kit.

He's the guy I bought my GTX from
I got to see his collection and the relay kits which he puts together. He builds to order so everything fits correctly. Top notch kits.

 

[Fran Blacker]

Had the bulkhead plug out and when plugged back in pushed contact to the inside of car.

 

[R/T]

A good grounding of the battery negative to the inner fender (to battery tray support bolt or whatever) would remove any bad ground doubt!

 

[rlem1977]

As Fran mentioned, working with aged wiring can be a challenge. Over time the electrical system becomes brittle, corroded, and fragile, plus we find someone else's hack jobs. Just disconnecting, moving, unplugging, etc. can cause hidden fraying or broken strands that can lead to degraded performance and even fires. Good luck with sorting out the issue.

 

[Wietse]

Wiring upgrade is a good thing on these cars, also keep potential fires in mind.
You could trace the electrical wiring to your headlights, follow the wiring diagram and measure the voltage at certain points.
Keep the multi meter - on the battery pole, and with the + you check voltage on different locations on the supply to the headlights.
Start at the alternator, you might see a big voltage drop across the bulkhead connector or somewhere else.
I know you serviced the bulk head connector, but using an old one stays a weak link IMO.

 

[Crackedback]

If you test for voltage drop, make sure you do it with the powered item connected and operating. Disconnecting the terminal and testing voltage with no load doesn't tell you much.

7 volts at the light is a HUGE issue. There is something very wrong in the system. Good grounds are a must.

@threewood Hope the GTX is treating you right.

 

[Wietse]

If you test for voltage drop, make sure you do it with the powered item connected and operating. Disconnecting the terminal and testing voltage with no load doesn't tell you much.

Good add-on...something quite important piece of information i failed to mention

 

[rrTor-Red]

He's the guy I bought my GTX from
I got to see his collection and the relay kits which he puts together. He builds to order so everything fits correctly. Top notch kits.

I have his kit. I put his relays under my battery tray and is out of sight, yet I can get there if need be

 

[Nacho-RT74]

Relays are a nice upgrade, but that doesn't mean you will be fixing the problem. With this I meant will find a fix the problem and then if you want make the upgrade for better, but stock system must work quite fine without the upgrade.

Halogen headlamps uses to demand the relay upgrade because the added load affects the headlight switch points inside. Wires and terminals are fine with it, but not points.

 

[Wietse]

I've installed 4ea H4 headlamps in my '69 Coronet with all new wiring harness, with engine off I have very bright lights, not dimmed for sure.
When engine at idle and switching on the headlight, incl. big beams does not cause a single interior light to slightly dim.
Load is little higher from what I calculated that time (don't remember the figures now) so a good wiring harness should be able to provide without the need of relay's.
I am running a 85 Amp alternator though.

 

[eric383]

One of the benefits of running a headlight relay besides brighter lights is you're not pulling 6 or more amps through the headlight switch. Just my 2 cents worth.

 

[Wietse]

Very true.
You cannot just go ahead and install a set of Halogen lights, you have to make sure your wiring is 100% and all contacts are clean, good grounds etc. etc.

Anyway, OP should trace the power source and measure individual sections (specially across the bulkhead connector and see where this massive voltage drop occurs.